Pressure-sensitive copying paper employing a phthalein compound color forming agent



United States Patent O 3,551,181 PRESSURE-SENSITIVE COPYING FAPER EM- PLOYING A PHTHALEIN COMPOUND COLOR FORMING AGENT Shiro Kimura, Teruo Kobayashi, and Sadao Ishige, Ka-

nagawa, and Isao Hirano and Toshiyuki Nita, Tokyo, Japan, assignors to Fuji Shashin Kabushiki Kaisha, Kanagawa, and Hodogaya Kagaku Kogyo Kabushiki Kaisha, Tokyo, Japan No Drawing. Filed June 20, 1967, Ser. No. 647,304 Claims priority, application Japan, June 24, 1966, 41/41,117 Int. Cl. B41m 5/22 U.S. Cl. 11736.2 4 Claims ABSTRACT OF THE DISCLOSURE A pressure-sensitive copying paper capable of producing orange-yellow colored markings in response to pressure and having a layer of rupturable microcapsules containing an oil in which a phthalein compound having the general formula:

X. [De o is dissolved. By also adding to the oil other conventional color forming agents, such as, a red-purple forming agent or a blue forming agent, a black copy can be obtained.

In the above compound R is a radical selected from the group consisting of hydrogen and lower alkyl groups containing less than carbon atoms and X and X are radicals selected from the group consisting of hydrogen and wherein at least one of X and X is and R and R are selected from the group consisting of lower alkyl groups, having less than 5 carbon atoms, and a benzyl group.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to pressure-sensitive copying paper using a phthalein compound as a color forming agent.

(2) Description of the prior art Ordinary pressure-sensitive copying paper is composed of an upper sheet, the back of which is coated with an electron donating, adsorbable and color developing colorless organic compound, designated as a color forming agent, hereinafter, contained in micro capsules, and a lower sheet, the surface of which is coated with an electron acceptive adsorbent. In use, the upper sheet is put upon the lower one and the capsules are ruptured by pressing, such as by handwriting or typewriting, whereby the oil carrying the colorless color forming agent is adsorbed on the electron acceptive, adsorbent to form a col- Patented Dec. 29, 1970 or. As the electron acceptive adsorbent, there are used solid acids or active clays, such as attapulgite, acid clay, zeolite and bentonite. On the other hand, a number of color forming agents, for example, Crystal Violet Lactone, are well known as color forming agents capable of forming red, blue and violet. (See, Dyes and Drugs published by Kaseihin Kogyo Kyokai, p. 8l4, No. 3; p. 9-13, No. 4; p. 17, No. 6, vol. 9, 1964.)

However, only a few color forming agents which are color-forming in the yellow-orange color range are known, for example, o-hydroxy-benzalacetophenone, 2-(4-hydroxy-styryl)-3; 3-dimethyl-3H-indole and 2-(4-acetoamidestyryl)-3,3-dimethyl-3H-indole. The first has the disadvantage that the color density is low and the latter two (cf. Belgian Pat. 648,567) have the disadvantage that they are not sufficiently light-proof before and after color formation.

Therefore, an object of the invention is to provide a pressure-sensitive copying paper, capable of forming yellow-orange colors, and also to provide a pressure-sensitive copying paper which can form black markings by using the yellow-orange color forming agent together with known red-purple and blue-forming agents.

The features of the color forming agent used in this invention are that it is colorless before color formation and stable in air. It rapidly gives a yellow-orange color when written on by a pen under pressure. The color density of the images formed is high and the images have excellent resistance to light and water. Moreover, it is found that, if the color forming agent is used jointly with a known color forming agent of red, violet, blue or blue green, 21 pressure-sensitive copying paper which forms back markings is obtained, without bad effects, such as desensitizing.

SUMMARY OF THE INVENTION Generally speaking, the color forming agent of this invention is represented by the following general Formula I:

in which X H, and

and

Xr=N and wherein R and R are lower alkyl groups having less than 5 carbon atoms, or benzyl groups, and R is hydrogen atom or a lower alkyl group, having less than 5 carbon atoms.

structural isomer of the same, represented by the following general Formula II, that is, which may be of 2-(4- dialkylaminobenzoyl)-triphenylcarbinol type corresponding to the structure in which the phthalein ring is opened:

liq

in which X X R R and R have the same meaning as in the general Formula I. In Chemical Abstracts, vol. 2, p. 2385 also, a phthalan compound is described having a structure in which X H, and

R1 XZZN in the general formula. Although the structural isomer does not appear in this literature, a 2-benzoyl-4-dialkylamino-triphenylcarbinol type, as represented by the general Formula 11 may be assumed as a structural isomer. The compounds described in Beilstein and Chemical Abstracts may be regarded as identical, since there is no difference in their synthesis methods and melting points. Our efforts to determine the structure lead to the conclusion that the phthalein type of the general Formula I is to be supported, rather than the ring-opened, structural isomer of the general Formula II, as described hereinafter. In this invention, therefore, the general Formula I is employed as the structure of the color forming agent, but the structural isomer of the general Formula II should not be necessarily excluded considering such various theories. This is the reason for use of the expression generally speaking.

DETAILED DESCRIPTION OF THE INVENTION Examples of the color forming agents used in the inven tion are shown below.

Color forming agent: Chemical name No. 1 3(or 1)-(4-dimethylaminophenyl-1,

1(0r 1,3)-diphenyl 3 hydroxyphthalein.

2 3(or 1)-(4-dimethylaminophenyl)-1,

1(0r 1,3)-diphenyl 3 methoxyphthalein.

. 3 3(or 1)-(4-dimethylaminophenyl)-1,

1(or 1,3) diphenyl 3 ethoxyphthalein.

3(or 1)-(4 diethylaminophenyl 1, 1(or 1,3)-diphenyl 3 hydroxyphthalein.

. 5 3(or 1) (4-diethylaminophenyl) 1,

1(or 1,3)-diphenyl 3 methoxyphthalein.

. 6 3(or 1)-(4-diethylaminophenyl) 1,

1(or 1,3) diphenyl 3 ethoxyphthalein.

3(or 1) (4-N-benzyl-N-ethylaminophenyl)-1, 1(or 1,3) diphenyl-3-hydroxy-phthalein.

4 Color forming agent Chemical agent No. 8 3(or 1)-(4benzyl N ethylaminophenyl)-1, 1(or 1,3) diphenyl-3- niethoxy-phthalein.

No. 9 3(or 1) (4-N-benzyl-N-ethylaminophenyl)-1, 1(or 1,3) diphenyl-3- ethoxy-phthalein.

No. 10 3(or 1) (4-N-benzyl-N-ethylaminophenyl)-1, 1(0r 1,3) diphenyl-3- propoxy-phthalein.

No. 11 3(or 1) (4-N-benzyl-N-ethylaminophenyl)-1, 1(or 1,3) diphenyl-3- butoxy-phthalein.

Compounds Nos. 111 are examples of the color forming agents represented by the general Formula I, but, if there are some structural isomers, as represented by the general Formula II according to the foregoing theory, the compound of No. 1, for example, may be 2-(4-dimethylaminobenzoyl)-triphenylcarbinol or 2-benzoyl-4-dimethylamino-triphenylcarbinol.

where R and R is a lower alkyl group, M is MgX, Na or Li. X is a halogen atom.

Examples of the synthesis of these color forming agents are as follows:

Synthesis of the color forming agent No. 1 is carried out by subjecting 2-methoxy(or ethoxy)carbonyl-4'dimethylaminobenzophenone or its tautomeric isomer, pseudometyl ester or Grignard reaction with phenylmagnesium bromide (or iodid) in great excess (more than 2 moles) in ether solution. M.P. 194 C. (cf. Beilstein vol. 14, p. 244, and Chemical Abstracts, vol. 2, p. 2385).

In the synthesis of the color forming agent No. 2, color forming agent No. 1 is heated in methyl alcohol, after adding one drop of hydrochloric acid. M.P. 158 C. (of. Beilstein, vol. 14, p. 245).

In the synthesis of the color forming agent No. 3, color forming agent No. 1 is heated in ethyl alcohol, after adding one drop of hydrochloric acid. M.P. 175 C. (cf. Beilstein, vol. 14, supplement I, p. 493).

In the synthesis of the color forming agent No. 4, 2- methoxy (or ethoxy) carb0nyl-4'-diethylaminobenzophenone is reacted with phenylmagnesium bromide in great excess (more than 2 moles) in ether solution. M.P. 160 C. (cf. Beilstein, vol. 14, supplement I, p. 493).

In the sytnhesis of the color forming agent No. 5, color forming agent No. 4 is methylated in methyl alcohol in the same manner as for color forming agent No. 2, M.P. l389 C. (cf. Beilstein, vol. 14, supplement I, p. 493).

In the synthesis of the color forming agent No. 6, color forming agent No. 4 is ethylated in ethyl alcohol in the same manner as for color forming agent No. 3. M.P. 118 C. (cf. Beilstein, vol. 14, supplement I, p. 493).

In the synthesis of the color forming agent No. 7, 2- methoxy( or ethoxy)carbonyl'4-N-benzyl-N-ethylaminobenzophenone is reacted with phenyl-magnesium in great excess -(more than 2 moles) in ether solution, as for color forming agent No. 1. M.P. 148-9 C.

In each of the above-mentioned synthesis examples, tetrahydrofuran may be used in place of ether as the reaction medium. The amount of phenylmagnesium. bromide used is varied from 2 mole equivalents to 5 mole equivalents, but the result of elementary analysis or nuclear magnetic resonance teaches that the phenyl group is always reacted only to the extent of 2 mole equivalents as described in the literature. Similar results are also obtained by the use of phenyllithium or phenylsodium in place of the phenylmagnesium bromide, amounting to more than 2 moles.

When 1 mole of 1-benzoyl-2-(4-dialkylaminobenzoyl)- benzene is reacted or condensed with 1 mole of benzene by heating in concentrated sulfuric acid, also, a compound of the general Formula I is obtained, but with a lower yield. This is similar to the method of preparing 1,2-bis-(4-dialkylaminobenzoyl)-benzene, described in Bei lstein, vol. 14, p. 245. A compound is obtained from the starting material, 2-alkoxycarbonyl-4'-dialkylaminobenzophenone, through the reaction of two phenyl groups with the carbonyl group of the 2-alkoxycarbonyl thereof and corresponds to 3-(4-dialkylaminophenyl)- 1,l-diphenyl-3 hydroxy(or alkoxy)-phthalein, described in Beilstein. That is, it is the structure in which and X =H in the general Formula I, or the structural isomer, 2-(4-dialkylaminobenzoyl)-triphenylcarbinol (or alkyl ether), the structure in which and X =H in the general Formula II. On the other hand, a compound, considered to be derived from the same starting material as the forementioned, through the reaction of two phenyl groups with the carbonyl group in 2-alkoxycarbonyl and in benzophenone one by one, corresponds to 1-(4-dialkylaminophenyl)-l,3-diphenyl-3- hydroxy (or alkoxy)-phthalein described in Chemical Abstracts. That is, it is the structure in which X =H, and

or the structural isomer, 2-benzoyl-4'-dialkylamino-triphenylcarbinol (or alkyl ether), the structure in which X =H and 7 R1 X2=N in Formula II.

The general Formula I is better supported than the formula of the structural isomer, because of the result of infrared analysis measured using a nujol as a solvent in which there is hardly viewed the absorption of C=O. The analysis of nuclear magnetism resonance also supports the same conclusion. That is to say, since H in OH of the color forming agent No. 1 (R=H in the general formula) is removed to a high magnetic field site, more so than H in OH of the triphenylcarbinol, the presence of O-COH (the phthalein ring in the general Formu la I is suggested, rather than CCOH, the carbinol part in the formula of the structure isomer. However, it is uncertain whether in the general Formula I by results of elementary analysis, ultraviolet absorption, infrared absorption and nuclear magnetic resonance.

In order to produce the pressure-sensitive copying paper of our invention by the use of the color forming agent aforementioned, it is preferred to employ the methods described in US. Pats. 2,548,366, 2,800,457 and 2,800,458, as is well known in the art. For example, the method of making microcapsules utilizing the phenomenon of complex coacervation may be employed. The invention is characterized by the use of a particular compound of the general Formula I (including the structural isomer) as a color forming agent, and the characteristics of the copying paper are independent of the method of making the copying paper. The addition amount of the color forming agent is ordinarily varied from 0.5 to 5% by weight of the oily solvent.

The following examples serve to illustrate the invention without limiting the same.

EXAMPLE 1 3 g. of the color forming agent No. 1 was dissolved in g. of diphenyl trichloride and the solution was added to a solution of 20 g. of gum arabic in 1 60 g. of water to be emulsified. 20 g. of an acid-treated gelatin in g. of water was then added thereto, to which acetic acid was added with stirring to lower the pH to 5, and 5 00- g. of water was added to cause coacervation, whereby a thickened liquid film of gelatin-gum arabic was formed around the oil drop containing the color forming agent. Subsequently, the pH was lowered to 4.4, and 3.8 g. of 37% formalin was then added for hardening.

The temperature was maintained at 50 C. throughout the foregoing operation. The mixture was then cooled to 10 C., for gelling the thickened liquid film and its pH was raised to 9 to increase the effect of hardening, followed by standing for several hours. The capsule forming operation was thus accomplished.

The resulting capsule solution was applied to a sheet of paper, by roll coating or by air knife coating, and was dried. The coated paper, as an upper sheet, was stacked on a clay paper, as a lower sheet, and was written upon under pressure. Color formation in yellow-orange colored markings appeared rapidly on the clay paper. The color of the yellow-orange markings did not fade, even if wetted with water or subjected to exposure to the direct rays of the sun for a long time. When the coated paper of the color forming agent (upper sheet) was sub jected to heating at 100 C., for 20' hours and to expos ure to the sun for a long time, no deterioration in the color forming characteristics was found. The resistances to light, water and heat, before and after color formation were saatisfied in use, even after the passage of a long time.

EXAMPLE 2 lESSfil'ltlflllY the same procedure used in Example 1 was followed except that 1.3 g. of the color forming agent No.

2 and known color forming agents, i.e., 0.3 g. of benzoyl leuco methylene blue, 0.6 g. of malachite green lactone, 0.2 g. of N-phenyl leuco auramine (blue color forming agent), 0.8 g. of crystal violet lactone and 0.4 g. of Rhodamine B anilinolactam (red color forming agent) were used as color forming agents. Color fonmation of black markings appeared rapidly on a clay paper. In the case of using the color forming agent No. 2 only, color formation of yellow-orange markings appeared. Instead of the above-mentioned known agents, a red-forming agent, such as, 3-dimethylamino-7-methylfluoran or 2- (4-dimethylarninostyryl) 3,3-dirnethyl-3H-1ndole, could be employed.

EXAMPLE 3 Essentially the same procedure used in Example 1 was followed except that 1.5 g. of the color forming agent No. 3, 1 g. of the color forming agent No. 4 and 2.5 g. of rhodamine B anilinolactam were used. Bright red markings were obtained. Rhodamine B anilinolactam used alone, resulted in violescent-red markings, which gave an unfavorable impression, in practice, due to the darkness. In the case of using the color forming agent No. 3 or No. 4 alone, excellent color formation of yelloworange markings appeared in each case, both being excellent in their heat resistance to light and water.

EXAMPLE 4 similar to Example 1.

EXAMPLE 5 The absorption maximum and optical density of our color forming agent, color-formed with 95% acetic acid (0.0006% solution), are shown in the following table. Thickness of the cell for measuring was 1 cm.

Second Absorption First subabsorpsubabsorption maximum tiou maximum maximum Color forming (optical (optical (optical agent density) density) density) No. 1 473 my (0.81) 445 I11); (055). 505 mu (0.65). No.2 473 mg (0.81) 445 my (0.55).. 505 Inn (0.65). No. 3 473 m (0.80) 445 my 505111;;(0 65) No. 4 475 I11}: (0.81) 446 In. (0.55). 507 my (0.66). No.5 475 m, (0 81 446 m (0.54) 507 m (0.65). No.6 475 1111:.(0 80) 446 m (0.53).. 507 my. (0.65). No 7 476111; (0.78).... 447 m (056),." 508111;;(064).

When the color forming agents Nos. 17 were color formed under pressure on a clay paper coated with an acid clay, in a manner similar to Example 1, each maximum of the reflection absorption was shifted to the side of longer wave length. Each maximum was about 5 m. longer than each absorption maximum of the above table.

What is claimed is:

1. A pressure-sensitive copying paper including a base sheet having thereon a layer of rupturable micro-capsules containing an oil having dissolved therein as a colorforming agent a phthalein compound represented by the general formula wherein R is selected from the group consisting of H and a lower alkyl group, having less than 5 carbon atoms, and

X and X are selected from the group consisting of H and where R and R are selected from the group consisting of a lower alkyl group, having less than 5 carbon atoms, and a benzyl group, at least one of said X and X being 2. The pressure-sensitive copying paper as claimed in claim 1 wherein said phthalein compound is selected from 3(or 1) (4-dimethylaminophenyl) 1,1(or 1,3)-diphenyl-3 hydroxy-phthalein, 3(or 1) (4-dimethylaminophenyl) 1,1(or 1,3) diphenyl 3 methoxy-phthalein, (3 or 1) (4 dimethylaminophenyl)-l,1(or 1,3) diphenyl 3 ethoxy-phthalein, 3(or 1) (4-diethylaminophenyl) 1,1(or 1,3) diphenyl 3-hydroxy-phthalein, 3(or 1) (4 diethylaminophenyl) 1,1(or 1,3)-diphenyl-3-methoxy-phthalein, 3(or 1) (4diethylaminophenyl)-],1(or 1,3) diphenyl 3 ethoxy-phthalein, 3(or 1)- (4 N benzyl N ethylaminophenyl)-l,l(or 1,3)-diphenyl 3 hydroxy phthalein, 3(or 1)-(4-N-benzy1-N- ethylaminophenyl) 1,1(or 1,3) diphenyl 3 methoxyphthalein, 3(or 1) (4-N-benzyl-N-ethyl aminophenyl)-1, 1(or 1,3)-diphenyl 3 ethoxy-phthalein, 3(or 1) (4- N benzyl-N-ethylaminophenyl)-1,1.(or 1,3)-diphenyl-3- propoxy-phthalein and 3(or 1) (4-N-benzyl-N-ethylannnophenyl)-1,1(or 1,3) diphenyl-3-butoxy-phthalein.

3. The pressure-sensitive copying paper as claimed in claim 1 wherein said oil encapsulated in the microcapsules further has dissolved therein a red-purple color-agent and a blue color-forming agent.

4. The pressure-sensitive copying paper as claimed in claim 3 wherein said red-purple-forming agent is selected from the group consisting of Rhodamine B anilinolactam, 3-d methylamino-7 methylfluoran and 2 (4-dimethylaminostyryl) 3,3 dimethyl 3H-indole, and said blueformmg agent is selected from leucomethylene blue, Malachite Green, Crystal Violet lactone and N-phenylleuco Auramine.

References Cited UNITED STATES PATENTS 3,268,537 8/1966 Gosnell et al. 11736.2 3,336,337 8/1967 Gosnell 117-36.2 3,389,007 6/1968 Oda et al 117-36.2 3,432,327 3/1969 Kane et al. 1l736.2

MURRAY KATZ, Primary Examiner US. Cl. X.R. 

